Wire coating oven apparatus



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United States Patent 3,351,329 WIRE COATING OVEN APPARATUS David W. Thomas, Indianapolis, Ind., assignor to General Electric Company, a corporation of New York Filed Oct. 20, 1965, Ser. No. 498,822 9 Claims. (Cl. 263-3) ABSTRACT F THE DESCLOSURE Wire coating apparatus including a housing having a solvent removal zone and a curing zone, and with a wire cooler near the wire exit opening of the housing. Adjustable pressure control plates are mounted between the two zones to control the pressure of airflow therebetween. Venturi pressure plate restricting means are mounted within the curing Zone adjacent the wire exit opening in order to maintain the internal pressure of the oven in the vicinity of the exit below the external environment.

This invention is generally related to apparatus for the coating of metals and more particularly to improved apparatus for efficiently removing solvents and other volatile components which are present in a coating material when applied, and for polymerizing or uniformly fusing the remaining components of the coating material to the metal. It is particularly applicable to an oven for the curing of coating material upon wire. An oven of the general type in which this invention might iind utility is disclosed in United States Patent 3,183,605 which issued to Donald D. Argue and lohn D. Staufer on an application tiled December 27, 1961, and which is assigned to the same assignee as the present invention.

In the process of coating metal Wires with materials such as enamels or resins, the coating material if often suspended in a solvent or dispersing agent which enables it to be applied evenly to the surface of the wires as they are passed therethrough. The wires are then passed through apparatus which removes the solvent or dispersing agent by evaporation and polymerizes or cures the remaining coating material to the wires to provide the necessary electrical and mechanical properties. Such apparatus may be comprised of an oven having a first treating zone for heating the coated wires to evaporate the solvent and a second treating zone for curing the coating material, and a wire cooler, which is usually located near the wire exit opening of the oven, to cool the coated wires after they have passed through the treating zones.

The evaporation of the solvent in the first treating zone of the oven produces noxious fumes which must be safely disposed of, because if these fumes escape to the exterior environment of the oven they create unpleasant working conditions for personnel in the immediate area. Therefore, such ovens often contain means for igniting these fumes, such as a catalytic burner, to produce additional heat within the oven, thereby aiding in the curing process as well as tending to eliminate by combustion the undesired fumes, and such ovens also often include exhaust means for removing a part of the fumes to an area where'they may be safely disposed of. However, a small portion of these fumes which are not exhausted often escape combustion. Because of the relatively hivher pressure within ovens of the prior art and the continuous movement of the wires through the oven and out the wire exit opening thereof, a pumping eTect is created. This pumping effect tends to cause these fumes to pass from the oven, via the wire exit opening, to the surrounding environment. In the past, various means have been utilized to prevent the escape of these fumes through the exit opening. One such means includes a pressure 3,351,329 Patented Nov. 7, 1967 ICS box placed between the exit opening of the oven and the entrance to the wire cooler and supplied with air under a pressure greater than that caused by the oven at the exit opening, thereby forcing air into the oven via the exit opening preventing the fumes from escaping through the opening. Such pressure boxes, whiletending to prevent the escape of fumes, occasionally cause turbulence and nonuniform temperatures and gas velocities in the curing zone near the exit opening. These conditions adversely atect the uniformity of cure of the coating material on the wires as they pass through this zone. This invention provides apparatus for controlling conditions within the curing zone. of a wire coating oven and within the cooling zone of a wire cooler in such manner as to overcome these problems, enabling uniform curing and cooling of the coating material on the wires while vpreventing vthe esca-pe of fumes to the lsurrounding en- -zone ofv a wire coating oven in such manner as to cause the internal pressure of the oven near the wire exit opening to be less than the pressure of the external environment.

I Another object of this invention is to provide means for controlling conditions within a wire coating oven in such manner as to prevent the escape of fumes therefrom to the external environment.

It is a further object of this inventionV to provide apparatus enabling improved control of conditions within the curing zone of a wire coating oven thereby producing a more uniform cure of the coating material upon wires passing therethrough while preventing the escape of fumes to the environment of the oven.

are provided for controlling the direction and velocity of "the curing airflow within the curing zone of a wire coat- "ing oven in such manner as to causel the internal pressure of the oven near the Wire exit opening to be mainltained at a level below that of its external environment. `This lower internal pressure at the Wire exit opening prevents the objectionabley fumes within the oven from escaping to the external environment, and produces a smooth ilow of air from the external environment through the wire exit opening into the curing zone. Heating means Vthe curing airllow, thereby preventing turbulence and are provided within the oven near the wire exit opening to heat this incoming flow of air prior to its-entry into nonuniform temperatures in the wire exit opening.

As used herein, the term curing airflow is intended to denotea mixture of heated air and various other gases including combustible vapors. A second aspect of the invention includes the provision ,of ltiow directing means within a Wire cooler which is usually positioned above a wire coating oven to cool the coated wire as it exits from the oven prior to being wound on suitable storage means. The liow directing means cause the pressure Within the wire cooler near the wire entrance opening thereof to be maintained at a level area surrounding the below that of lits external environment. This lower internal pressure at the entrance to the wire cooler causes external air to ow into this entrance and prevents the cold air stream within the wire cooler from owing or spilling out of this entrance into the curing zone of the oven via its wire exit opening located immediately below the wire cooler.

These aspects of the invention also cooperate to eliminate the need for, and the inherent disadvantages of, a pressure box between a wire coating oven and an associated wire cooler.

Further aspects of my invention will become apparent hereinafter, and the specification concludes with claims particularly pointing out and distinctly claiming the sub- 'ject 4matter which I regard as my invention. The invention, however, as to organization and method of operation, together with further objects and advantages thereof, may best be understood by reference to the following description when taken in conjunction with the accompanying drawings in which:

FIGURES la and lb are sectional side views of an oven and wire cooler, respectively, incorporating the features of this invention;

FIGURE 2 is a sectional detail view in perspective of a feature of the invention located at the top of the solvent removal zone wire slot within `the oven of FIGURE 1a;

FIGURE 3 is a sectional detail view of a feature of the invention Within the Wire cooler of FIGURE 1b;

FIGURE 4 is a sectional perspective view of the upper portion of the oven of FIGURE la, showing in greater detail various features of the ow control means of the invention;

FIGURE 5 is a partially sectioned front view of the upper portion of the oven of FIGURE 1a and includes a portion of the front of the wire cooler of FIGURE 1b; and

FIGURE 6 is a sectional detail view of one of a plurality of distribution control units incorporated in the invention which are shown in broken lines in the front view of FIGURE 5.

Referring now to the drawings, wherein like reference characters designate like or corresponding parts throughout the several views, there is shown in FIGURE 1a, in section, a wire coating oven 11 having two treating zones, namely a lower solvent removal zone and an upper curing zone. Strands of wire 12 to be coated pass from a supply Vmeans 13, such as a reel or drum, through a coating means 14 which applies the desired coating material suspended in a solvent or dispersing agent. The coated strands of wire 12 then pass through an entrance slot 10 at the bottom of oven 11 and into the solvent removal zone thereof. In passing upward through the solvent removal zone, the coating material is heated by radiant panels 15 and 16 and by a stream of heated air which is produced by heat- Ving air taken into the oven via suitable vent means in the inthe upper curing zone. This simultaneous application of both radiant heating and convection heating in the solvent removal zone of wire coating ovens is disclosed in United States Patent 3,183,604, which issued to Iohn D. Staufr'er on an application led December 27, 1961, and which is assigned to the same assignee as the present invention. The strands of wire 12 and the heated airow containing the vaporized solvent pass from the solvent removal zone through an adjustable pressure control means 19 (shown in detail in FIGURE 2) into the curing zone.

The strands of coated wire 12 continue to pass upward through the curing zone wire slot 21 and out the wire exit opening 22 at the top of oven 11, while a curing airow is established. within the curing zone in the direction indicated by t-he flow arrows. As shown by these flow arrows in FIGURE la, the curing airflow within the curing zone wire slot 21 is in a downward direction while the movement of the coated wire is in an upward direction. This curing airflow is established and controlled in the following manner. The heated airflow containing the fumes of vaporized solvent removed fromthe coating material in the solvent removal zone passes upward through adjustable pressure control means 19. This feature of the invention, which may be seen in greater detail in FIGURE 2, is comprised of a pair of adjustable plates which run the full width of the oven and may be adjusted by suitable means 23, such as an elongated slot and bolt arrangement, to vary the size of the wire slot opening between the solvent removal zone and the curing zone. By adjusting pressure control means 19 to reduce the size of the wire slot opening at this location, the pressure of the heated airow entering the curing zone may be reduced, allowing the curing airflow to be more easily established in the desired downward direction in curing zone wire slot 21. As this heated airrow containing the vaporized solvent passes through pressure control means 19 into the curing zone, suitable blower means 24 and exhaust means 25 cause it to be pulled past catalytic burner means, comprised of a catalyst 26 and a burner 27, which ignites it producing additional heat within the curing airflow. A portion of this heated air, approximately equal to the amount of fresh air being pulled into the oven by blower means 18 in the solvent removal zone, is exhausted by exhaust means 25 to an area where it may be safely disposed of,

vwhile the balance of the heated air is directed by blower air distribution nozzle means 29. This feature of the int vention extends the full width of the oven and directs the curing airflow into the curing zone wire slot 21. As may be seen in FIGURE 4, nozzle means 29 is separated into a plurality of equally spaced chambers by separating walls 31. At the entrance opening to each of these chambers from passageway 28 is located a distribution control unit 32 (also shown in FIGURES 4 and 5, and in detail in FIGURE 6). These distribution control units 32 each include a panel or door member 33 which may be adjustably raised or lowered, thereby reducing or enlarging the effective size of the entrance opening of its associated chamber, by raising or lowering the attached control rod 34 which extends through the top of oven 11. Control rods 34 are shown in the various gures of drawing as having T handles and locking means 35 for individual manual adjustment; however, it is to be understood that each control rod 34 may be coupled to a motor or other mechanism for remote control purposes. By individually adjusting distribution control units 32, the ternperature and velocity of the curing airflow within each of the chambers of nozzle means 29 may be balanced with respect to one another. This balancing of the curing airflow just prior to its discharge from nozzle means 29 into the curing zone wire slot 21 aids in preventing turbulence and uneven temperatures or hot spots in wire slot 21, thereby providing more uniform fusing or curing of the coating material upon the strands of wire 12 as they pass through the curing zone.

As may be seen in FIGURE 4, nozzle means 29 has a support member 36 in the center of the exit opening of each of its chambers. These support members add structural rigidity to nozzle means 29 and provide attaching points, in addition to those provided by separat ing walls 31, for attaching a honeycomb grid means 37 which further improves the uniformity of ow of the curing airflow as it is discharged from nozzle means 29 into wire slot 21. Also, the bottom plate member of nozzle means 29 extends out into the wire slot 21 and has faces 38 and 39 shaped so as to provide pressure plate means for producing a restriction in wire slot 21. Another pressure plate-restriction producing means 41 running the full width of the oven is located on the wall of wire slot 21 opposite the exit opening of nozzle means 29. The pressure plate means formed by faces 38 and 39 of nozzle means 29 cooperate with pressure plate means 41 and nozzle means 29 such that the curing airow discharged from nozzle means 29 passes through these restrictive pressure plate means in a downward direction producing a venturi action which reduces the pressure in wire slot 21 above the exit opening of nozzle means 29. This venturi action causes the pressure in wire slot 21 near the wire exit opening 22 to be maintained at a level below that of the external environment of oven 11. This lower internal pressure at wire exit opening 22 prevents objectionable fumes within the curing airflow from escaping to the external environment, and produces a smooth iiow of outside air, through wire exit opening 22, into wire slot 21 Where it joins the curing airow. The cooler outside air owing into wire slot 21 is heated by heating means 42 and 43 (see FIGURES la, 4 and 5), which extend the full width of the oven and are attached to the walls of Wire slot 21 near the wire exit opening 22. This heating prevents the cooler incoming air from adversely aifecting the uniformity of cure of the coating material on the strands of wire 12 and also prevents turbulence and uneven temperatures in wire slot 21 in the area where this incoming air combines with the curing airow discharged from nozzle means 29.

After passing through the curing zone of oven 11 and out the wire exit opening 22 at the top thereof, the heated strands of wire 12, with the coating material cured thereon, pass through outside air for a short distance as shown in FIGURE 5. They then enter a wire cooler 51 (see FIGURE lb) located above oven 11 via an entrance opening S2. The strands of wire 12 continue to move upward through a cooling slot 53 and out the top of wire cooler 51 to be wound on suitable storage means. A cooling airflow established by a blower means S4 passes through duct means 55 to passageway 56 of wire cooler 51. As shown by the flow arrows in FIGURES 1b and 3, the cooling airow passes downward through passageway 56 and then upward through another feature of the invention, flow directing means, into wire slot 53 to cool strands of wire 12 as they pass upward therethrough. These ow directing means, which are shown in detail in FIGURE 3, comprise a honeycomb grid means 57, a vertically adjustable panel means 58 which may be adjusted by suitable means 59, such as an elongated slot and bolt arrangement, for varying the size of the opening 61 through which the cooling airflow passes in order to enter cooling slot 53, and a pressure plate-restriction producing means 62 located opposite opening 61 for providing a restriction in cooling slot 53. Grid means 57, adjustable panel means 58, and restrictive pressure plate means 62 extend the full width of the wire cooler and cooperate in such manner that the cooling airliow discharged through opening 61 produces, in conjunction with restrictive pressure plate means 62, a venturi action which yreduces the pressure in cooling slot 53 below the restrictive means 62 to a level below that of the external environment of wire cooler 51. This lower internal pressure at entrance opening 52 causes external air to flow into this entrance and prevents the cooling airflow within cooling slot 53 from flowing or spilling out of entrance opening 52 into the curing zone of oven 11 via its wire exit opening 22 located immediately therebelow.

Thus it may be seen from the foregoing description and accompanying drawings that this invention provides apparatus for use in wire coating ovens and wire coolers which enable more uniform curing and cooling of coating materials upon wires passing therethrough while preventing the escape of fumes from such ovens to the surrounding environment and preventing the escape of cold air from wire coolers into the curing zone of associated wire ovens. This invention thereby eliminates the need for a pressure box between a wire coating oven and a Wire cooler. It should be realized that certain aspects of this invention may eiiiciently and beneficially be incorporated in other types of ovens, furnaces, and similar devices utilizing moving airflows.

While in accordance with the patent statutes, I have described what at present is considered to be the preferred embodiment of my invention, it will be obvious to those skilled in the art that various changes and modiiications may be made therein without departing from my invention, and I, therefore, aim in the following claims to cover all such equivalent variations as fall within the true spirit and scope of this invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. Wire coating apparatus comprising: a Wire coating oven including la housing; a solvent removal zone in said housing, said housing having a wire entrance opening to enable coated wire to enter said housing and pass through said solvent removal zone; means in said housing for producing a heated airflow within said solvent removal zone to evaporate solvents contained in the coating material of coated wire passing through said solvent removal zone; `a curing zone in said housing adjacent said solvent removal zone; means in said housing for producing a heated curing airflow within said curing zone for curing the coating material on said coated wire as it passes from said solvent removal zone through said curing zone, said housing having a wire exit opening to allow said coated wire to pass from said housing, adjustable pressure control means within said housing for controlling the pressure of said heated airflow entering said curing zone from said solvent removal zone; air distribution nozzle means within said curing zone having a plurality of separate chambers therein; a plurality of distribution control units adjacent said nozzle means for providing individual control of the heated curing airow through said separate chambers to adjust the temperature and velocity of said-heated curing airflow within each of said chambers; pressure plate-restriction producing means within said curing zone cooperating with said air distribution nozzle means to produce a venturi action to maintain the internal pressure of said oven near said wire exit opening at a level below that of its external environment thereby causing external air to ow into said oven through said wire exit opening; heating means within said curing zone near said wire exit opening to heat said external air iiowing through said wire exit opening into said oven; and a wire cooler ladjacent said oven, said wire cooler including a cooling chamber having an airiiow opening, blower means for producing a cooling airflow in said cooling chamber, an inlet aperture for admitting said coated wire lafter its passage through said wire coating oven, an outlet aperture for allowing said coated wire to pass therefrom after being cooled by said cooling airow, means in said cooling chamber for vary-l ing the size of said cooling airflow opening, and means cooperating with said cooling airflow opening for providing a venturi action in said cooling airflow thereby to maintain the internal pressure of said cooling chamber near said inlet aperture at a level below that of its external environment to allow external air to flow into said inlet aperture.

2. Wire coating apparatus comprising a wire coating oven including a housing, a solvent removal zone in said housing, said housing having a wire entrance opening to enable coated wire to enter said housing and pass through said solvent removal zone, means in said housing for producing a heated airflow within said solvent removal zone to evaporate solvents contained in the coating material of coated Wire passing through said solvent removal zone,

-a curing zone in said housing adjacent said solvent removal zone, means in said housing for producing a heated curing airflow within said curing zone for curing the coating material on said coated wire as it passes from said solvent removal zone through said curing zone, said -housing having a wire exit opening to allow said coated wire to pass from said housing, -air distribution nozzle means within said curing zone having a plurality of separate chambers therein, -a plurality of distribution control units adjacent said nozzle means, said distribution control units providing individual control of said separate chambers for adjusting the temperature and velocity of said heated curing airow within each of said chambers to minimize turbulence and uneven temperatures in said curing zone, means within said curing zone cooperating with said air distribution nozzle means to produce a venturi action for maintaining the internal pressure of said oven near said wire exit opening at a -level below that of its external environment thereby to cause external vair to tlow into said oven through said wire exit opening, and a wire cooler adjacent said oven, said wire cooler including la cooling chamber having a cooling airflow opening and blower means for producing a cooling airflow, said cooling charnber including an inlet aperture and an outlet aperture for allowing said coated wire to pass therefrom after being cooled by said cooling airflow, adjustable panel means in said chamber for varying the size of said cooling airflow opening, and means in said cooling chamber for providing a venturi action to maintain the internal pressure of said cooling chamber near said inlet aperture at a level below that of its external environment to cause external air to flow into said inlet aperture and thereby prevent the cooling airilow from spilling out of said cooling chamber via said inlet aperture into said wire coating oven.

3. Wire coating apparatus comprising: a wire coating oven including a housing, said housing having a wire entrance opening to enable coated wire to enter said housing and a wire exit opening to allow said coated wire to pass from said housing; a solvent removal zone in said housing; means in said housing for producing a heated airiiow within said solvent removal zone to evaporate solvents contained in the coating material of coated wire passing through said slovent removal zone; a curing zone in said housing adjacent said solvent removal zone; means in said housing for producing a heated airflow within said curing zone for curing the coating material on said coated Wire as it passes from said solvent removal zone through said curing zone; control means within said housing for controlling the pressure of said heated airflow entering said curing zone from said solvent removal zone; nozzle means within said curing zone, said nozzle means having a plurality of separate chambers; a plurality of distribution control units adjacent said nozzle means for providing individual control of the heated airflow through each of said separate chambers; means within said curing zone cooperating with said air distribution nozzle means for producing a venturi action to maintain the internal pressure of said oven near said wire exit opening at a level below that of its external environment thereby to cause external air to flow into said oven through said wire exit opening; heating means within said curing zone near said wire exit opening to heat said external air flowing through said metal exit opening into said oven to prevent said external air from adversely affecting the uniformity of cure of the coating material on said coated wire; and a wire cooler near said wire exit opening, said wire cooler comprising a cooling chamber including an inlet aperture for admitting said coated wire after its passage through said wire coating oven and an outlet aperture for allowing said coated wire to pass therefrom, blower means for producing a cooling airflow through said cooling chamber, flow directing means in said cooling chamber for maintaining the internal pressure of said cooling chamber near said inlet aperture at a level Abelow that of its external environment thereby to cause external air to flow into terial of coated wire passing through said solvent removal zone, a curing zone in said housing adjacent said solvent removal zone, means in said housing for producing a heated curing airilow within said curing zone for curing the coating material on said coated wire as it passes from said solvent removal zone through said curing zone, control means located within said housing intermediate said curing zone and said solvent removal zone for controllingk the pressure of said heated airflow entering said curing zone from said solvent removal zone, air distribution nozzle means within said curing zone having a plurality of separate chambers therein, a plurality of distribution control units for providing control of each of said separate chambers to adjust the temperature and velocity of said heated curing airow within each of said chambers, pressure plate-restriction producing means within said curing zone cooperating with said air distribution nozzle means to produce a venturi action to maintain the internal pressure of said oven near said wire exit opening at a level below that of its external environment and cause external air to enter through said wire exit opening, and heating means mounted within said curing zone adjacent said wire exit opening to heat said external air entering through said wire exit opening and to prevent said cool external air from adversely affecting the uniformity of cure of the coating material upon said coated wire.

5. In wire coating apparatus, a wire cooler comprising a blower means for producing a cooling airow, a cooling chamber coupled to said blower means Afor receiving said cooling airflow, said cooling chamber including a cooling airow opening, an inlet aperture for admitting coated wire to be cooled and an outlet aperture for allowing said coated wire to pass therefrom after being cooled by said cooling airflow, adjustable panel means in said chamber for varying the size of said cooling airflow opening, and means in said chamber for cooperating with said cooling airilow opening for producing a venturi action to maintain the internal pressure of said cooling chamber near said inlet aperture at a level below that of its external environment and cause external air to flow into said inlet aperture.

6. Wire coating oven comprising: a housing, said housing having a wire entrance opening to enable coated wire to enter said housing and a wire exit opening to allow said coated wire to pass from said housing; a solvent removal zone in said housing; means in said housing for producing a heated airow within said solvent removal zone to evaporate solvents contained in the coating material of coated wire passing through said solvent removal zone; a curing zone in said housing adjacent said solvent removal zone; means in said housing for producing a heated curing airow within said curing zone for curing the coating material on said coated wire as it passes from said solvent removal zone through said curing zone, flow control means within said housing for maintaining the internal pressure of said oven near said wire exit opening at a level below that of its external environment to cause external air to flow into said oven through said wire exit opening; and heating means within said curing zone between said wire exit opening and said ow control means for heating said external air flowing through said wire exit opening into said oven to thereby prevent said external air `from adversely affecting the uniformity of cure of the coating material upon said coated wire.

7. A wire coating oven including a housing, a solvent removal zone in said housing, said housing having a wire entrance opening to enable coated wire to enter said housing and pass lthrough said solvent removal zone, means in said housing for producing a heated airflow Within said solvent removal zone to evaporate solvents contained in the coating material of coated wire passing through said solvent removal zone, a curing zone in said housing adjacent said solvent removal zone, means in said housing for producing a heated curing airflow within said curing zone for curing the coating material on said coated wire as it passes from said solvent removal zone through said curing zone, said housing having a wire exit opening to allow said coated wire to pass from said housing, venturi tlow control means mounted within said housing adjacent said wire exit opening for maintaining the internal pressure of said oven near said wire exit opening at a level below that of its external environment causing cool external air to flow into said oven through said wire exit opening, and heating means disposed within said curing zone between said wire exit opening and said venturi flow control means for heating said cool external air flowing through said metal exit opening into said oven to prevent said cool external air from adversely aiecting the uniformity of cure of the coa-ting material upon said coated wire.

S. A wire coating oven comprising a housing, said housing having a wire entrance opening to enable coated wire to enter said housing and a wire exit opening to allow said coated wire to pass from said housing, a solvent removal zone in said housing, means in said housing for producing a heated airow within said solvent remoi/a1 zone to evaporate solvents contained in the coating material of coated wire passing through said solvent removal zone, a curing zone in said housing adjacent said solvent removal zone, means in said housing for producing a heated curing airflow within said curing zone for curing the coating material on said coated wire as it passes from said solvent removal zone through said curing zone, plate means -adjustably mounted in said housing intermediate said solvent removal zone and said curing zone for controlling the pressure of said heated airflow entering said curing zone from said solvent removal zone, nozzle means within said curing zone, distribution control means cooperating with said nozzle means for providing control of said heated curing airflow, and pressure reducing iiow means disposed within said curing zone cooperating with said nozzle means for producing a venturi action thereby maintaining the internal pressure near said Wire exit opening at a level below that of its external environment and causing external air to ow into said oven through said wire exit opening.

9. Wire `coating oven comprising: a housing having a wire entrance opening -to enable coated wire to enter said housing and a wire exit opening to allow said coated wire to pass from said housing, a solvent removal zone in said housing; means in said housing for producing a heated airiiow within said solvent removal zone to evaporate solvents contained in the coating material of coated wire passing through said solvent removal zone, a curing zone in said housing adjacent said solvent removal zone, means in said housing for producing a heated curing airflow within said curing zone for curing the coating material on said coated wire as it passes from said solvent removal zone through said curing zone, means within said housing for controlling the pressure of said heated airflow entering said curing zone from said solvent removal zone, nozzle means within said curing zone, airflow restriction means within said curing zone cooperating with said nozzle means to produce a venturi action in said heated curing airilow to maintain the internal pressure of said oven near said wire exit opening at a level below that of its external environment thereby causing external air to ow into said oven through said wire exit opening, and heating means disposed within said curing zone intermedi-ate said wire exit opening and said airilow restricting means to heat said external air owing through said wire exit opening into said oven.

References Cited UNITED STATES PATENTS lll/1963 Harris 263-3 5/1965 Argue et al. 263--3 X 

6. WIRE COATING OVEN COMPRISING: A HOUSING, SAID HOUSING HAVING A WIRE ENTRANCE OPENING TO ENABLE COATED WIRE TO ENTER SAID HOUSING AND A WIRE EXIT OPENING TO ALLOW SAID COATED WIRE TO PASS FROM SAID HOUSING; A SOLVENT REMOVAL ZONE IN SAID HOUSING; MEANS IN SAID HOUSING FOR PRODUCING A HEATED AIRFLOW WITHIN SAID SOLVENT REMOVAL ZONE TO EVAPORATE SOLVENTS CONTAINED IN THE COATING MATERIAL OF COATED WIRE PASSING THROUGH SAID SOLVENT REMOVAL ZONE; A CURING ZONE IN SAID HOUSING ADJACENT SAID SOLVENT REMOVAL ZONE; MEANS IN SAID HOUSING FOR PRODUCING A HEATED CURING AIRFLOW WITHIN SAID CURING ZONE FOR CURING THE COATING MATERIAL ON SAID COATED WIRE AS IT PASSES FROM SAID SOLVENT REMOVAL ZONE THROUGH SAID CURING ZONE, FLOW CONTROL MEANS WITHIN SAID HOUSING FOR MAINTAINING THE INTERNAL PRESSURE OF SAID OVEN NEAR SAID WIRE EXIT OPENING 